It is well known that water-soluble copper compounds such as copper gluconate and copper citrate have a bad breath inhibiting effect and a dental plaque adherence inhibiting effect. Conventionally, various oral compositions having a water-soluble copper compound blended were proposed as in U.S. Pat. Nos. 3,044,939, 3,565,933, 3,655,868 and 4,112,066 and Japanese Patent Application Kokai Nos. 56-169619, 56-169620, 60-193910, 61-37720, 61-143317, 62-142109, 1-153620 and 1-153622.
However, water-soluble copper compounds are unstable in aqueous solutions and apt to form insoluble matters due to the oxidation of themselves or the reaction with other components coexistent in the aqueous solutions.
Thus, a transparent liquid oral composition having such a water-soluble copper compound blended would become turbid or produce sediments after a long-term storage because of the formation of the insoluble matters, resulting in injuring the transparent appearance of the product.